U.S. patent application number 11/072703 was filed with the patent office on 2005-09-08 for full duplex communication system using disjoint spectral blocks.
This patent application is currently assigned to InterDigital Technology Corporation. Invention is credited to Chitrapu, Prabhakar R..
Application Number | 20050195758 11/072703 |
Document ID | / |
Family ID | 34994161 |
Filed Date | 2005-09-08 |
United States Patent
Application |
20050195758 |
Kind Code |
A1 |
Chitrapu, Prabhakar R. |
September 8, 2005 |
Full duplex communication system using disjoint spectral blocks
Abstract
The invention involves utilizing pieces of disjoint spectral
blocks. In one embodiment, a frequency division duplex approach is
used, where each spectral block is utilized solely for either
uplink or downlink communications. In another embodiment, a time
division duplex approach is used, where each spectral block is time
divided and uplink and downlink communications are assigned to
different time slots within the same spectral blocks. In another
embodiment, a code division duplex approach is utilized, where
uplink and downlink communications are assigned different
codes/hopping patterns within a same spectral block.
Inventors: |
Chitrapu, Prabhakar R.;
(Blue Bell, PA) |
Correspondence
Address: |
VOLPE AND KOENIG, P.C.
DEPT. ICC
UNITED PLAZA, SUITE 1600
30 SOUTH 17TH STREET
PHILADELPHIA
PA
19103
US
|
Assignee: |
InterDigital Technology
Corporation
Wilmington
DE
|
Family ID: |
34994161 |
Appl. No.: |
11/072703 |
Filed: |
March 4, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60550492 |
Mar 5, 2004 |
|
|
|
Current U.S.
Class: |
370/279 |
Current CPC
Class: |
H04B 7/2615 20130101;
H04L 5/14 20130101; H04L 27/2601 20130101; H04W 74/006 20130101;
H04W 72/0453 20130101; H04W 88/08 20130101; H04W 74/004 20130101;
H04B 7/2618 20130101; H04L 47/17 20130101 |
Class at
Publication: |
370/279 |
International
Class: |
H04B 007/14 |
Claims
What is claimed is:
1. A method for utilizing disjoint spectral blocks comprising: time
dividing each of the disjoint spectral blocks into time slots;
providing uplink and downlink communications to communicate over
the disjoint spectral blocks; and assigning the uplink and downlink
communications to time slots of the disjoint spectral blocks, where
any of the uplink or downlink communications can potentially be
assigned to any time slot of any disjoint spectral block available
for assignment.
2. The method of claim 1 further comprising spreading the assigned
uplink and downlink communications over substantially the entire
frequency range of the spectral block.
3. The method of claim 2 wherein the spreading is performed by
direct sequence spreading.
4. The method of claim 2 wherein the spreading is performed by
orthogonal frequency division multiplex.
5. The method of claim 1 further comprising spreading the uplink
and downlink communications in a fixed spectrum size and wherein at
least one of the disjoint spectral blocks carries a different
number of the fixed spectrum sizes than another one of the disjoint
spectral blocks.
6. A method of utilizing disjoint spectral blocks comprising:
providing uplink and downlink communications to communicate over
the disjoint spectral blocks; dynamically assigning a first
spectral block for uplink communications and a second spectral
block for downlink communications, wherein in subsequent dynamic
assignments the first spectral block is potentially assigned for
downlink communications and the second spectral block is assigned
for uplink communications; and assigning at least one of the
provided uplink communications to the first spectral block and at
least one of the provided downlink communications to the second
spectral block.
7. The method of claim 6 wherein the first and second spectral
blocks have different spectrum sizes.
8. The method of claim 5 further comprising dynamically spreading
the uplink and downlink communications to substantially fit within
the different spectrum sizes.
9. The method of claim 8 wherein the spreading is performed by
direct sequence spread spectrum and the dynamic spreading is
performed by changing a chipping rate of the spreading.
10. The method of claim 8 wherein the spreading is performed by
direct sequence spread spectrum and the dynamic spreading is
performed by filtering a result of a direct sequence spread
spectrum operation.
11. The method of claim 8 wherein the spreading is performed by
frequency hopping spread spectrum and the dynamic spreading is
performed by changing a hopping pattern.
12. The method of claim 11 wherein the hopping pattern spans at
least two of the spectral blocks.
13. The method of claim 11 wherein the frequency hopping spread
spectrum is slow frequency hopping spread spectrum.
14. The method of claim 8 wherein the spreading is performed by
orthogonal frequency division multiplex and the dynamic spreading
is performed by nulling sub-carriers or restricting a number of
used sub-carriers.
15. The method of claim 6 wherein the dynamically assigning is
based on an amount of downlink and uplink traffic and the size of
each disjoint spectral block.
16. A method of utilizing disjoint spectral blocks comprising:
providing uplink and downlink communications to communicate over
the disjoint spectral blocks; dynamically assigning the uplink and
downlink communications to any of the disjoint spectral blocks,
each communication assigned to one of the spectral blocks is
assigned a unique code/hopping pattern, wherein potentially an
uplink and downlink communication are assigned hopping patterns
with common frequencies within one of the disjoint spectral
blocks.
17. A method of utilizing disjoint spectral blocks comprising:
providing uplink and downlink communications to communicate over
the disjoint spectral blocks; assigning the uplink and downlink
communications to different hopping patterns, where the assigned
hopping pattern of an uplink communication and the assigned hopping
pattern of a downlink communication potentially use frequencies in
the same disjoint spectral block at the same time and the assigned
hopping patterns span at least two of the disjoint spectral blocks.
Description
CROSS REFERENCE TO RELATED APPLICATION(S)
[0001] This application claims priority from U.S. Provisional
Application No. 60/550,492, filed on Mar. 5, 2004, which is
incorporated by reference as if fully set forth herein.
FIELD OF INVENTION
[0002] This invention relates to wireless communications. More
particularly, it relates to wireless communications in multiple
frequency bands.
BACKGROUND
[0003] New pieces of frequency spectrum have been allocated for
wireless communications. For example, a reallocation proposed by
the U.S. Federal Communications Commission would allocate 27
megahertz of spectrum from the 216-220 Mhz, 1390-1395 Mhz,
1427-1429 Mhz, 1429-1432 Mhz, 1432-1435 Mhz, 1670-1675 Mhz, and
2385-2390 Mhz bands, by transfer of these bands from government to
non-government use. FIG. 1 is an illustration of the 1390-1395 Mhz,
1427-1429 Mhz, and 2385-2390 Mhz spectrum blocks. These spectral
pieces are not contiguous, are small in size, and may be of unequal
widths.
[0004] Accordingly, it is desirable to have more efficient
approaches to utilizing disjoint spectrum blocks.
SUMMARY
[0005] The invention involves utilizing pieces of disjoint spectral
blocks. In one embodiment, a frequency division duplex approach is
used, where each spectral block is utilized solely for either
uplink or downlink communications. In another embodiment, a time
division duplex approach is used, where each spectral block is time
divided and uplink and downlink communications are assigned to
different time slots within the same spectral blocks. In another
embodiment, a code division duplex approach is utilized, where
uplink and downlink communications are assigned different codes
within a same spectral block. The codes may be used to spread the
signal in frequency by chopping the signal in time domain or by
hopping the center frequency in a pseudo random manner within the
available bandwidth. In the last embodiment, a judicious
combination of these methods (Frequency, Time and Code Division
Duplexing techniques) may be employed.
[0006] In order to practically realize such systems, the
communicating radio devices need to be able to flexibly and
efficiently reconfigure themselves into being able to transmit and
receive in various spectral bands while using various techniques.
As such, in a preferred embodiment, the communicating radio devices
in such contexts, may be implemented in software using principles
such as Software Defined Radio (SDR) or using reconfigurable
hardware architectures, such as programmable array architectures
and programmable parallel and streaming processors.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is an illustration of disjoint FCC proposed spectrum
blocks.
[0008] FIG. 2 is a simplified block diagram of a transmitter and a
receiver for use in adaptive frequency division duplex
communication.
[0009] FIG. 3 is a simplified block diagram of a transmitter and a
receiver for use in adaptive time division duplex
communication.
[0010] FIG. 4 is a simplified block diagram of a transmitter and a
receiver for use in adaptive code division duplex
communication.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0011] As used herein, the terminology "wireless transmit/receive
unit" (WTRU) includes but is not limited to a user equipment,
mobile station, fixed or mobile subscriber unit, pager, STA, or any
other type of device capable of operating in a wireless
environment. The terminology "base station" includes but is not
limited to a Node B, site controller, access point or any other
type of interfacing device in a wireless environment.
[0012] DSSS, FHSS, OFDM FDD
[0013] One approach for using non-contiguous frequency bands is a
frequency division duplex based approach. The available frequency
bands are adaptively assigned for the uplink or the downlink. The
assignment of the bands may be based on the amount of traffic and
the size of the bands. Additionally, interference measurements may
be used to determine whether the uplink or downlink should be
assigned to a particular band. To illustrate, one band may
experience severe interference in the uplink and mild interference
in the downlink. This one band should preferably be used for the
downlink. While the usage of a frequency band for uplink and
another frequency band for downlink is known prior art, in this
invention we are proposing a scheme where (1) in case only a pair
of frequency bands is used for duplex communication, the widths of
the uplink and downlink frequency bands need not be equal to each
other, (2) in case more than two non-contiguous bands of
frequencies are being used for the duplex communication, more than
one non-contiguous frequency band may be used for uplink or
downlink. In other words, the uplink (or downlink) data is split
into and transmitted on different frequency bands. The data under
consideration may be data from/to the same or different user(s),
data from the same or different source (e.g. video file
download).
[0014] FIG. 2 is a simplified diagram of a transmitter 10 and a
receiver 20 for use in adaptive frequency division duplex
communication. The transmitter 10 and receiver 20 may be located in
a WTRU, base station or both. At the transmitter 10, data is
received for transmission. A frequency band controller 18
determines which frequency band or bands are used for the
transmissions. By adaptively assigning uplink and downlink
communications to certain bands, traffic asymmetry can be handled
better. To illustrate, a smaller sized frequency band could be
allocated to a low traffic uplink, while a larger sized frequency
band allocated to a heavy traffic downlink. A spread spectrum
device 12 processes the data for transmission. If the frequency
bands are of unequal spectrum, the spread spectrum device 12
produces a signal to fit in the corresponding frequency band.
[0015] To illustrate, one spread spectrum technique is direct
sequence spread spectrum (DSSS). In DSSS, a chip code sequence is
mixed with the data to produce a spread signal. To produce a signal
of the desired spectrum size, the chipping rate or filtering
coefficients can be adjusted to control the spread. Alternately,
the spread signal may be filtered (bandpass, lowpass, highpass,
etc.) to fit into the desired frequency band. In this case, the
receiver may experience a degraded performance in synchronizing to
the spreading code, due to the energy filtered and hence not
transmitted to the receiver. Thus, a careful engineering tradeoff
is preferably utilized in the design of this approach. At the same
time, this approach provides clear advantages over the prior art,
as traditional spread spectrum systems transmit the entire band of
spread frequencies whereas the present invention provides a
receiver with a code synchronizer that only has partial spectral
information.
[0016] In another approach, the spread spectrum is fixed, such as
1.5 MHz. The number of DSSS frequencies put into a frequency band
is based on the size of the band. To illustrate, a 2 MHz band may
have one 1.5 MHz DSSS frequency and a 5 MHz band may have 2 or 3
1.5 MHz DSSS frequencies.
[0017] If the data is being sent over two non-contiguous bands, the
spread spectrum device may spread the data multiple times at the
same chipping rate (for equal sized spectrums) or at different
chipping rates for different sized spectrums. Alternately, as noted
above, the data may be spread over a spectrum spanning both
frequency ranges and the non-assigned frequencies are notch
filtered out of the resulting spread signal.
[0018] Another spread spectrum technique is frequency hopping
spread spectrum (FHSS). In FHSS, the data hops over many relatively
narrowband frequencies within one or multiple ones of the assigned
frequency bands. The frequency hopping pattern is constrained to
fit within the assigned frequency bands. To illustrate, two
frequency bands may be assigned for the uplink. The frequency hop
pattern may hop both frequency bands.
[0019] Preferably, slow frequency hopping modulation is used. Using
slow FHSS reduces the spill energy outside of the allocated bands
within which the frequencies hop (leaving some guard bands).
However, faster frequency hopping may be desirable in certain
implementations.
[0020] Another spread spectrum technique is orthogonal frequency
division multiplex (OFDM). In OFDM, multiple overlapping but
orthogonal carriers are used to carry the data. For an OFDM
transmission, the number of sub-carriers can be restricted or
nulled to control the spectrum used by the resulting signal. To
illustrate, the OFDM transmission may be assigned to two
non-contiguous, but otherwise closely spaced frequency bands. The
spread OFDM signal may span both frequency bands with the carriers,
nulled within the frequency band between the two assigned bands.
Alternately, a different OFDM waveform may be produced for each
frequency band.
[0021] The resulting spread spectrum signal is modulated to the
appropriate frequency by a dynamic modulator 14 and radiated by an
antenna 16 or antenna array. The dynamic modulator 14 is capable of
modulating the spread spectrum signal to any of the frequency
bands.
[0022] The receiver 20 receives the radiated signal using an
antenna 22 or antenna array over the frequency bands 30. A dynamic
demodulator 24 demodulates the received signal to an intermediate
frequency. The dynamic demodulator 24 is capable of demodulating
from any of the frequency bands. A despreading device 28 despreads
the intermediate frequency signal to recover the transmitted data.
The demodulated frequencies and the despreading device 28 are
controlled by a frequency band controller 26.
[0023] Although the components of FIG. 2 are illustrated as
separate components, these components may be on an integrated
circuit (IC), such as an application specific integrated circuit
(ASIC), multiple ICs, discrete components, or a combination of
discrete components and IC(s).
[0024] DSSS OFDM TDD
[0025] Another approach for using non-continuous frequency bands
for duplex communications is a time division duplex based approach.
The available frequency bands are time divided, such as into time
slots, and the time slots are adaptively assigned for the uplink or
the downlink.
[0026] FIG. 3 is a simplified diagram of a transmitter 10 and a
receiver 20 for use in adaptive time division duplex communication.
The transmitter 10 and receiver 20 may be located in a WTRU, base
station, or both. At the transmitter 10, data is received for
transmission. A frequency band/time controller 38 determines which
frequency band(s) and time slot(s) are used for the transmissions.
The assigned frequency band(s)/time slot(s) are preferably
adaptively assigned to be used for uplink and downlink across all
the frequency bands. The time slot allocation is preferably done
considering all of the frequency bands. Such an approach can lead
to better management of channel assignments, such as slow dynamic
channel allocation and radio resource management. The adaptation
process may be based on the traffic characteristics, RF
interference scenarios, and WTRU and network capabilities.
[0027] A spread spectrum device 12 processes the data for
transmission. DSSS or OFDM, among other techniques may be used for
the spreading. The spread signal is modulated to the appropriate
frequency band(s) by a dynamic modulator 14. A switch 32 allows the
communication to be radiated by the antenna 16 in the appropriate
time slot(s).
[0028] The receiver 20 receives the radiated signal using an
antenna 22 or antenna array over the frequency bands/time slots 36.
A switch 34 effectively couples the antenna output to the remaining
receiver components during the appropriate time slot(s). A dynamic
demodulator 24 demodulates the received signal to an intermediate
frequency. A despreading device 28 despreads the intermediate
frequency signal to recover the transmitted data. The demodulated
frequencies, the despreading device 28, and switch 34 are
controlled by a frequency band/time controller 40.
[0029] Although the components of FIG. 3 are illustrated as
separate. components, these components may be on an integrated
circuit (IC), such as an application specific integrated circuit
(ASIC), multiple ICs, discrete components, or a combination of
discrete components and ICs.
[0030] DSSS FHSS CDD
[0031] FIG. 4 is a simplified diagram of a transmitter and a
receiver for use in adaptive code division duplex communication.
The transmitter and receiver may be located in a WTRU, base
station, or both. At the transmitter, data is received for
transmission. In adaptive code division duplex, uplink and downlink
communications are separated by channelization codes or frequency
hop patterns. The uplink and downlink communications can exist
simultaneously in the same frequency band. However, the uplink and
downlink are assigned different channelization codes or hop
patterns to minimize interference between the uplink and downlink
communications within the frequency band.
[0032] A frequency band/code controller 42 determines which
frequency band(s) and code(s) are used for the transmissions. The
assigned frequency band(s)/code(s) are preferably adaptively
assigned to be used for uplink and downlink. The adaptation process
may be based on the traffic characteristics, interference
considerations, and network capabilities.
[0033] A spread spectrum device 12 processes the data for
transmission. DSSS or FHSS, among other techniques may be used for
the spreading. For DSSS, the assigned channel code is used in the
spreading. For FHSS, the assigned code controls the hopping
pattern. The spread signal is modulated to the appropriate
frequency band(s) by a dynamic modulator 14 and radiated by the
antenna 16 or antenna array.
[0034] The receiver 20 receives the radiated signal using an
antenna 16 or antenna array over the frequency bands/channelization
codes 46. A dynamic demodulator 24 demodulates the received signal
to an intermediate frequency. A despreading device 28 despreads the
intermediate frequency signal to recover the transmitted data. To
distinguish the desired signal from other signals, the despreading
device 28 uses the appropriate code for the despreading, such as a
channelization code for DSSS or hop pattern for FHSS. The
demodulated frequencies and the despreading device 28 are
controlled by a frequency band/code controller 44.
[0035] Although the components of FIG. 4 are illustrated as
separate components, these components may be on an integrated
circuit (IC), such as an application specific integrated circuit
(ASIC), multiple ICs, discrete components, or a combination of
discrete components and ICs.
[0036] Space Division Duplex (SDD) Scheme
[0037] In yet another embodiment of the present invention, the
spatial domain may also be used for utilizing non-contiguous
frequency bands. Consider a MIMO (multiple input multiple output)
antenna system. Here, the antennas at the transmitter and receiver
are spatially separated. The present invention proposes to use
different frequency bands to different antenna elements, thereby
using the multiple non-contiguous frequency bands in a simple and
efficient manner. This scheme is applicable for both duplex (i.e.
two-way) communications as well as broadcast/multicast (i.e.
one-way) communications.
[0038] Efficient Implementation of WTRUs
[0039] The WTRUs for such communication systems as disclosed in the
present invention are designed to be flexible reconfigurable
devices, for maximum amount of system efficiency. For example, as
the frequency bands are adaptively controlled for varying
functions, the WTRU will need to be adaptively reconfigured to be
able to transmit and receive on varying spectral bands using
varying duplexing techniques. Thus, in a preferred embodiment, a
Software Defined Radio (SDR) or Reconfigurable HW/SW approach using
programmable array architectures and/or programmable
parallel/streaming processors is utilized.
[0040] Although the features and elements of the present invention
are described in the preferred embodiments in particular
combinations, each feature or element can be used alone (without
the other features and elements of the preferred embodiments) or in
various combinations with or without other features and elements of
the present invention. Further, the present invention may be
implemented in any type of wireless communication system.
* * * * *